The invention relates to struts, more particularly to frictional damping struts that are spring biased and have cooperating wedge members for damping a movement.
Shock absorbers and struts and more particularly frictional damping struts are used to absorb and damp oscillatory movements in a number of applications. Applications include vehicles and machinery that are subject to repetitive oscillatory movements and vibration. Generally, a load is absorbed by a spring means while oscillations are absorbed and damped by viscous or frictional movement of cooperating parts.
Representative of the art is U.S. Pat. No.2,429,140 (1947) to Snyder which discloses a shock absorber having a friction unit actuated by an expander.
Also representative of the art is U.S. Pat. No. 4,606,442 (1986) to Paton et al. which discloses an assembly comprising damper shoes that are guided by and wedged transversely between two wedge rings.
Frictional damping strut assemblies may be incorporated into a tensioner assembly. A tensioner may be used to preload an engine drive belt in order to maximize operational efficiency and to minimize noise and vibration during belt operation.
Representative of the art is U.S. Pat. No. 5,951,423 (1999) to Simpson which discloses a mechanical friction tensioner having spring loaded wedge-shaped blocks and friction damping. The tensioner has a wedge-shaped piston that interacts with spring biased wedge-shaped blocks. As the piston moves inward the wedge-shaped blocks are pushed outward to provide friction damping.
The prior art damping struts are relatively complex and do not afford asymmetric damping.
What is needed is a damping strut having cooperating simplified wedge members. What is needed is a damping strut having a simplified wedge member providing proportional frictional damping. What is needed is a damping strut providing asymmetric damping. What is needed is a tensioner having a damping strut having a simplified wedge member. The present invention meets these needs.
The primary aspect of the invention is to provide a damping strut having cooperating simplified wedge members.
Another aspect of the invention is to provide a damping strut having a simplified wedge member providing proportional frictional damping.
Another aspect of the invention is to provide a damping strut providing asymmetric damping.
Another aspect of the invention is to provide a tensioner having a damping strut having a simplified wedge member.
Other aspects of the invention will be pointed out or made obvious by the following description of the invention and the accompanying drawings.
The invention comprises a frictional damping strut. The strut comprises an inner cylinder that slides within an outer casing. A spring biases the inner cylinder away from the outer casing in an axial direction. A first wedge member cooperatively engages a second wedge member. The first wedge member having a frictional engagement with the inner cylinder such that when the inner cylinder is pressed into the outer casing the first wedge member bears upon the second wedge member causing the first wedge member to radially expand, thereby increasing a frictional force between the first wedge member and the inner cylinder. A second spring preloads the first wedge member against the second wedge member. A belt tensioner may incorporate the damping strut to preload a belt and damp belt oscillations.